Analog Devices / Maxim Integrated LTC9105 IEEE 802.3af/at/bt PoE PD Controller
Analog Devices LTC9105 IEEE 802.3af/at/bt Power over Ethernet (PoE) Powered Device (PD) Controller has input current, voltage, and power telemetry. The LTC9105 includes an I2C interface to read telemetry, power sourcing equipment (PSE) allocated power, auxiliary input status, and to write power input priority. The LTC9105 also features a configurable downstream power-up disable with under-power indication when the PSE allocated power is less than the PD requested power.
The Analog Devices LTC9105 utilizes an external, low RDS(ON), N-Channel, Hot Swap MOSFET, and a 50mΩ current sense resistor. It supports the LT4321 ideal bridge to extend end-to-end power delivery efficiency. Also included are a power good output, an external signature resistor, a programmable resistor classification, and a pin-configurable PD requested Class. An auxiliary power supply is sensed at the AUX pin and reported through the I2C interface. Automatic maintenance of the power signature (MPS) circuitry keeps the PD interface powered when the downstream current draw falls below an internal MPS threshold.
Two dedicated delta-sigma analog-to-digital controllers (ADCs) continuously measure PD controller input voltage and current with a typical conversion time of 100ms and 14-bit resolution. Simultaneous conversion of current and voltage measurements enables high-accuracy power calculations.
Features
- IEEE 802.3bt PD controller
- 400kHz I2C interface
- Continuous voltage, current, and power telemetry
- Dedicated 14-bit delta-sigma current and voltage ADCs
- Automatic Maintain Power Signature (MPS)
- Supports up to 90W PDs with extended power
- 5-event classification sensing with PSE allocated power readback
- Seamless switchover between dual PD or PD/AUX inputs
- Superior surge robustness (100V absolute maximum)
- Wide -40°C to 125°C junction temperature range
- External Hot Swap N-channel MOSFET for lowest power dissipation and high system efficiency
- 50mΩ current sense resistor
- Auxiliary input sense with standby modes
- 20-pin 5mm x 5mm QFN package
Applications
- IEEE 802.3bt PDs with power telemetry
- Wireless access points/pico cells
- Internet Protocol (IP) security cameras
- Power over Ethernet (PoE) lighting
Typical Application
Development Tool
Analog Devices / Maxim Integrated EVAL-LTC9105-AZ Evaluation Board
This board features the LTC9105, MAX5974C, LT4321 controllers, and the ADuM1252 I2C isolator.